Method for activating a network component of a vehicle network system

ABSTRACT

A method and system for activating at least one temporarily inactive network component of a network system for a vehicle, in particular a motor vehicle. A central network device of the network system is connected via signals to the network components by a path inside the network system, the path extending at least partially across a network segment of the network system. The network segment connects via signals the network component and a first activation device associated therewith to a switch device arranged in the path and to a second activation device associated therewith in an unbranched manner. The central network device responds to the first activation device by the switch device by sending a network function control signal.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of application No. PCT/EP2011/052456,filed on 18 Feb. 2011. Priority is claimed on German, Application No.:10 2010 008 818.8, filed 22 Feb. 2010, the content of which isincorporated here by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for activating at least onetemporarily inactive network component of a network system for avehicle, especially for a motor vehicle.

2. Prior Art

Known network systems for vehicles, particularly motor vehicles, arebased in most cases on serial bus systems. An example of such a bussystem for networking various control devices for implementingsystem-wide functions of a vehicle is an asynchronous, serial bus systembased on a CAN bus (Controller Area Network). Another example is a LIN:Local Interconnect Network Bus System. Since electrical power issupplied in many vehicles by an energy store of limited storagecapacity, it is desirable that non-active parts of the network do notabsorb any power or absorb as little power as possible.

In the bus systems used in the field of application for vehicles, anenergy detection concept is used. The entire bus system is initiallyinactive. An energy pulse on the bus line of the bus system that leadsto the controller “waking up” and activating the entire system as aconsequence. In this context, the energy pulse can be a data frame oralso a single voltage pulse. In this system, the demand for quiescentcurrent is extremely low but all components connected to the bus systemare activated and “wake up”.

For stationary networks, the “Wake on LAN” standard (WOL) has beenestablished for some time (LAN: Local Area Network). It enables inactivehosts in the network to be selectively woken by the so-called magicpacket, an Ethernet frame that contains the MAC address of the host tobe woken and which is recognized by the corresponding host Ethernetcontroller.

However, this technology is unsuitable for use in the automotive ormotor vehicle field since the network controllers themselves must beactive or at least partially active to recognize such a packet. As aresult, the demand for quiescent current is distinctly too great for anautomotive environment.

SUMMARY OF THE INVENTION

It is an object of one embodiment of the present invention is to providea method for activating at least one temporarily inactive networkcomponent of a network for a vehicle in which individual networkcomponents can be activated selectively.

In the method according to one embodiment of the invention, a centralnetwork device of the network system is connected via signals to thenetwork component via a path inside the network system. The path leadsat least partially across a network segment of the network system, thenetwork segment connecting via signals the network component and anassociated first activation device unbranched to a switch devicearranged in the path and to an associated second activation device, andthe central network device addressing the activation device by theswitch device by sending a network function control signal. The centralnetwork device of the network system has, in particular, a networkmanager module.

The network component is an electrical device, particularly a controldevice of a vehicle component of the vehicle, preferably of the motorvehicle. To minimize the energy demand of the vehicle, the electricaldevice is temporarily inactivated when it is not needed.

In a network system of particularly simple structure, the centralnetwork device of the network system is connected via signals to thecorresponding network component via, in each case, one path within thenetwork system, the respective path leading completely via acorresponding network segment. In this network system, the centralnetwork device has the switch device itself or is connected via signalsto it by another network segment.

Whilst the network segment is unambiguously allocated to the respectivenetwork component, the other network segment can be allocated to aplurality of network components.

The network function control signal is preferably at least one voltagepulse that is applied by one component (network device, switch deviceand/or network component) to the signal line of the correspondingnetwork segment.

According to a preferred embodiment of the invention, the firstactivation device activates the network component after receipt of thenetwork function control signal and subsequently in turn sends out afurther network function control signal to the second activation devicefor confirming the activation.

According to a further preferred embodiment of the invention, it isprovided that the second activation device brings the switch device intoa transmitting/receiving state after receipt of the further networkfunction control signal. With this step, the activation is completelyfinished and the network component can communicate bidirectionally withthe switch device via the associated network segment.

According to a preferred embodiment of the invention, the network is anEthernet network. In an Ethernet network, the network components and acentral network device (e.g. as hosts), switch devices, and acorresponding network structure with network segments allocated torespective hosts are already known. The network function control signalis designed, for example, as NLP (NLP: Normal Link Pulses).

According to a preferred embodiment of the invention, the network systemhas a tree topology formed by the central network device, the at leastone switch device, and the network components. This topology isparticularly suitable for implementing the method according to oneembodiment of the invention. As an alternative, the network systempreferably has a mesh topology.

In particular, the network component and/or the network device is acontrol device of a vehicle component or at least part of such a controldevice.

The invention also relates to a network system of a vehicle, especiallya motor vehicle, preferably for carrying out the aforementioned methodand suitable for activating at least one temporarily inactive networkcomponent. The network system according to one embodiment of theinvention has a central network device connected via signals to thenetwork component via a path within the network system, the path leadingat least partially across a network segment of the network system andthe network segment connecting via signals the network component and anassociated first activation device unbranched to a switch devicearranged in the path and to an associated second activation device, andthe central network device addressing the first activation device by theswitch device by sending a network function control signal.

The network component is an electrical device, particularly a controldevice, of a vehicle component of the vehicle, preferably of the motorvehicle. To minimize the power requirement of the vehicle, theelectrical device is temporarily inactivated when it is not needed.

According to a preferred embodiment of the invention, the network is anEthernet network. In an Ethernet network, network components and acentral network device (e.g. as hosts), switch devices, and acorresponding network structure with network segments, which areallocated to respective hosts, are already known.

According to a preferred embodiment of the invention, it is providedthat the network system has a tree topology formed by the centralnetwork device, the at least one switch device, and the networkcomponents. This topology is particularly suitable for implementing themethod according to the invention. As an alternative, the network systempreferably has a mesh topology.

In particular, the network component and/or the network device is acontrol device of a vehicle component or at least part of such a controldevice.

Finally, the invention also relates to a motor vehicle comprising anaforementioned network system, particularly an Ethernet network.

BRIEF DESCRIPTION OF THE DRAWINGS

In the text which follows, one embodiment of the invention will beexplained in an exemplary manner referring to the drawing. However, theinvention is not restricted to the exemplary embodiment shown. In thedrawing:

FIG. 1 is a block diagram of a network system according to oneembodiment of the invention;

FIG. 2 is a network function control signal designed as so-called“normal link pulses”;

FIG. 3 is a block diagram of a network system according to oneembodiment of the invention;

FIG. 4 is a state diagram of a so-called “port state machine” of anetwork system; and

FIG. 5 is a block diagram of a network system according to the inventionin accordance with a further embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a diagrammatic structure of a network system 10 accordingto one embodiment of the invention with a tree topology formed by acentral network device 12, a plurality of switch devices 14 and aplurality of network components 16. In this arrangement, the networksystem 10 is designed as Ethernet network. The central network device 12comprises a host 18, a network manager 20 (network manager module), aswitch manager 22 (switch manager module) and a switch 24. The centralnetwork device 12 is connected via signals via a network segment 26 to anetwork component 18 and via three other network segments 28 to threeswitch devices 14 with switch 24, switch manager (switch managermodule), 22 and host 18. The switch devices 14 are in turn connected viasignals via network segments 26 to network components 16 and via othernetwork segments 28 to other switch components 14, producing the treestructure.

To each of the network components 16, a first activation device 16′designed as a so-called “energy detection module” is allocated and toeach of the switch devices 14, a second activation device 14′ designedas an “energy detection module” is allocated. The power consumption ofthe first activation device is less than the power consumption of theassociated active network components 16, the power consumption of thesecond activation device is less than the power consumption of theassociated active switch device 14 and of the associated central networkdevice, respectively.

FIG. 2 shows the sequence in time of network function control signals30, designed as rectangular pulses (more precisely so-called NLPs—NormalLink Pulses) for testing the state of a connection (of a link) in anEthernet network. For this purpose, a voltage U_diff is plotted againsttime t in a graph. The network function control signals 30, that is tosay the pulses 32 (NLPs), have a pulse width of 100 ns and a pulsespacing of 16 ms+/−8 ms.

According to one embodiment of the invention, these network functioncontrol signals 30 are used for activating a temporarily inactivenetwork component 16 and for confirming the activation.

The following function results within a network system 10 in which acentral network device 12 is connected via signals to the temporarilyinactive network component 16 via a path inside the network system 10.The path leads at least partially across a network segment 26 of thenetwork system 10 and the network segment 26 connects, via signals, thenetwork component 16 and an associated first activation deviceunbranched to a switch device 14 arranged in the path and to anassociated second activation device. The following steps are provided:

-   -   the central network device 12 addresses the first activation        device of the network component 16 by the switch device 14 by        sending a network function control signal 30,    -   the first activation device activates the network component 16        after receipt of the network function control signal 30 and        subsequently in turn sends out a further network function        control signal 30 to the second activation device of the switch        device 14 for confirming the activation, whereupon    -   the second activation device brings the switch device 14 into a        transmitting/receiving state after receipt of the further        network function control signal 30.

In the text which follows, the resultant concept will be described againusing a different terminology.

A Switched Ethernet consists physically of point-to-point connections.Thus, an energy detect principle can be applied individually forindividual hosts 18. It would not wake up the entire network since onlyone host 18, especially a network component 16, and one switch port (notshown in detail) of the switch device 14 are connected physically to aline (the network segment 26).

By selectively controlling the activity on a link, a host 18, especiallya network component 16, can accordingly be activated or deactivatedselectively. For this purpose, the switch 24 has to switch therespective port on or off. When the port is switched on, link pulses(NLPs) 32 are applied to the line (the network segment 26).

The link pulses 32 can be detected by an activation device designed asenergy detect module and their presence can be indicated by anelectrical output. The state of this output can trigger a wake-up (anactivation) or a shut-down (an inactivation).

The ports are configured by the switch manager (the switch managermodule) 22. This is software responsible for the entire configuration,monitoring, and control of a switch 24. Each port of a switch 24 ismodeled and treated by the switch manage 22 as a finite state machine.

The network manager (the network manager module) 20 forms thecenterpiece of the concept. It is the central management node that hasthe job of configuring and monitoring the entire network (network system10). This software has the overview of the entire topology of thenetwork 10 and of the state of the individual hosts 18. It cancommunicate with the individual switch managers 22 and thus allowindividual hosts 18 to be activated and deactivated selectively.

The overall concept represents the interactions between the threeindividual modules (central network device 12 with network manager 20,network component 16 with first activation device and switch device 14with switch manager 22 and second activation device).

The first question arising with respect to the structure of the networkmanagement is whether this is a centralized or distributed managementarchitecture. Although distributed management offers greaterreliability, it is significantly more complex and difficult to handle.In addition, the necessary communication between the distributedmanagement nodes causes additional data load. As a rule, a simple,uncomplicated management concept is the better choice. It is in thissense that the concept used here is also designed.

For this reason, the management concept presented is central (withcentral network device 12). Thus, the network manager 20 is a centralentity and not distributed over a number of network nodes. As alreadymentioned, network manager 20 is responsible for all management tasksconcerning the network. Network manager 20 knows the topology of thenetwork 10 and knows the state of all hosts 18 located in the network.Within the context of the present concept, only the power managementfield is covered but the network manager 20 can also handle all othernecessary management functions.

At the next level of hierarchy, there is an arbitrary number of switchdevices 14 with switches 24. These are “managed switches” having anarbitrary number of ports. The switch manager 22 of the switch device 14is responsible for configuring and controlling the switch 24 and cancommunicate with other network nodes.

At the ports of these switches 24, other switches 24 can be connected asthe next level of hierarchy. In this context, there can be an arbitrarynumber of such hierarchy levels. The end points of these tree branchesare the hosts 18. The switches 24 themselves can also be located on hostdevices (hosts 18) and form the switch devices. The switch manager 22and the host software can run as two processes on one and the same CPU.

The switch manager 22 represents the communication partner of thenetwork manager 20. If a node is to be activated, the network manager 20contacts the corresponding switch (manager) 22, 24, to which therelevant node is connected, and requests activation of the correspondingport. Thus, each active switch manager 22 must have a valid path to thenetwork manager 20.

As shown in FIG. 1, it is possible to configure the network 10 as a treehaving an arbitrary number of hierarchy levels.

The root of the tree is the central network device 12 with networkmanager 20 and switch 24, to which it is connected. The following levelsconsist of hosts (end points) 18 or other switch devices 14 withswitches 24 and, as a rule, with hosts 18 as interfaces to therespective next hierarchy level.

The port via which a switch 24 is connected to the next hierarchy levelabove will be called root port (analogously to the designation in theSpanning Tree protocol) in the text which follows. It is important thateach active manageable node with switch manager 22 needs a validconnection to the network manager 20.

In the text which follows, some basic principles, on which the powermanager concept is based, will be described in detail.

The network function control signals 30 shown in FIG. 2, designed aslink pulses or NLPs, respectively, are short voltage pulses applied by asubscriber in the Ethernet to its transmitting line of network segments26, 28 whilst there is no transmitting traffic. Control signals 30 areused for testing the state of the link. A subscriber detects a linkerror when no pulses 32 and no data traffic are received for 50 ms-150ms. In the case of 10 BASE-T Ethernet, these pulses 32 are called LinkIntegrity Test (LIT) pulses, in the case of 100 BASE-TX and autonegotiation, they are called Normal Link Pulses (NLP). Auto negotiation(100 BASE-TX) uses a sequence of up to 33 such pulses 32, thecommunication parameters of the transmitter (speed, full- orhalf-duplex) being encoded in this sequence. These sequences are called“Fast Link Pulse (FLP) bursts”.

The basic shape of the NLPs is shown in FIG. 2. The precisespecification of the pulse shape can be read up about in IEEE 802.3Clause 14.3.1. The Link Integrity Test itself (that is to say also thesequence in time of pulses 32) is specified in IEEE 802.3 Clause14.2.1.7 (page 321).

The FLP bursts which are used for auto negotiation have the same shapebut at a maximum, only 33 and at a minimum, 17 such pulses are sentspaced apart by 125 μs. The bursts are also spaced apart by 16 ms+/−8ms.

If the PHY of a port is activated, it sends out such pulses. Dependingon the configuration of the switch/controller (IOOSASE-TX), as FLPbursts (auto negotiation) or as NLPs, if auto negotiation isdeactivated.

The Energy Detect Module (EDM) is a system capable of detecting NLPs orFLP bursts, and indicating their presence in a suitable form. It isnecessary for each port on each device, i.e. a 4-port switch must havefour EDMs or one EDM with four inputs and outputs. The EDM must beconnected to the Rx line of the port but must not influence thereception of frames.

Advantageously, all IP addresses of the Ethernet network are static andknown to the network manager (or the corresponding software,respectively). However, the concept is not restricted to this. Thepossibilities for issuing IP addresses are open. For example, dynamicassignment by means of DHCP would be possible. The way in which thenetwork manager learns the IP addresses of the hosts 18 is open.

Furthermore, it is provided with advantage that in the initial state ofthe network system 10, the network manager module 20 and the associatedswitch 24 of the central network device 12 are always active. This ismade clear again by the active role of the central network device 12 inthe method for activating the temporarily inactive network component ofa network system. Although this permanent activity is not absolutelynecessary since a device activated from “outside”, during an attempt ofestablishing a connection to the network manager 20, would mandatorilyactivate the device, but as a rule, the network management software willwish to establish a type of basic state of the network 10, i.e. activateselected control devices. The concept is not restricted to this, either.

To provide a simpler description, the processes running in the networksystem (network) 10 to activate and deactivate hosts 18 andpart-networks can be considered at two levels, namely the hardware leveland the software level.

At the hardware level, the manner in which hosts 18 and switches 24physically activate one another, deactivate one another, and can benotified by an external activation/deactivation is specified.

At the network level, it is defined how shutdown and wake-up processes(deactivation and activation processes) are running in the network,using the mechanisms specified at the hardware level.

Whilst the hardware level thus defines how two adjacent network nodes(hosts 18 and switches 24) interact with one another physically, thenetwork level specifies the principle according to which a node in thenetwork can activate an arbitrary other node via the network managementsoftware, how the network management software activates the node and howit can deactivate a node.

Interactions at the Hardware Level

Two adjacent nodes, for example a switch 24 and a host 18, must becapable of activating one another when it is necessary, to inform oneanother about any activation that has taken place or to deactivate oneanother when it is demanded by the network manager 20.

The switch manager 22 treats each port of its switch 24 as a finitestate machine (FSM). By this model, a port can be controlled andmonitored in a simple manner. Thus, a manager of a 4-port switchsimultaneously manages four mutually independent FSMs. Firstly, themodel will be explained briefly here. After that, it is explained byusing a state machine how the individual mechanisms of the hardwarelevel are running.

Each port has four normal states:

-   -   UP means that the PHY of the respective port is in the        activated, normal state and a valid link exists. Both sides        (switch and host) transmit and receive NLPs and can transmit        frames if required.    -   DOWN designates the deactivated state of the port. The PHY is in        the power-down state, no NLPs are transmitted, data cannot be        transmitted.    -   HOST STARTUP is a state of transition in which the PHY is        activated and applies NLPs to the transmitting line. The host        connected to the port is not yet active and does not yet send        any link pulses. Thus, no valid link is recognized yet by the        switch 24.    -   HOST SHUTDOWN is also a state of transition, this time for        shutting down a connected host 18. The port PHY is deactivated        and does not send any NLPs. The host 18 is, however, still        active and sends NLPs which are indicated by the EDM of the        port.

Furthermore, there are two error states:

-   -   LINK FAIL indicates that a previously valid link has        unexpectedly broken down.    -   ERROR is a global error state into which the system changes on        the occurrence of other errors, the type or cause of the error        being stored.

Activating a host 18 designed as network component 16 by a switch occursas follows.

A switch 24 must be capable of activating a deactivated host 18connected to it on request of the network manager 20. The so-called“port state machine” shown in FIG. 4 meets this requirement.

If the network manager 20 requests the activation of the host 18, thisleads to a state transition into the HOST STARTUP state. In thiscontext, the PHY of the port is activated and begins to send NLPs. Thestate machine remains in this state as long as no NLPs are received fromthe host 18.

If the EDM of the host 18, that is to say the first activation device,detects the link pulses 32 (NLPs) of the switch device 14, it triggersthe booting process of host 18 in a suitable manner. As soon as theEthernet controller of host 18 is started, its PHY begins in turn tosend link pulses 32. These are detected by the EDM of the switch, thatis to say the second activation device, and indicated. This event leadsto a change of state of the FSM into the UP state. Both sides detectNLPs, that is to say the link is valid and the connection has beenestablished. It is now possible to transmit frames.

If an error occurs during the booting process of host 18 and no NLPs aresent back, a time out event takes place, the finite state machine (FSM)changes into the global error state and indicates a STARTUP_TIMEOUT.

Notification of the switch device 14 about an external activation byhost 18 occurs as follows.

If a host 18 is not activated following an initiative of the networkmanager 20 but from the outside or by a user, respectively, and if itsswitch 24 is still deactivated, the host 18 must inform its switch aboutthis so that it activates its port PHY.

The finite state machine (FSM) is in the DOWN state. As soon as thenetwork controller of host 18 begins to send NLPs, these are detected bythe EDM of the switch and indicated. This leads to a change of statefrom DOWN to UP, the PHY of the port being activated and in turn sendingNLPs. Both sides will now detect NLPs, the link is valid and frames canbe transmitted.

Activation of the switch device by host 18 occurs as follows.

As soon as the network controller of host 18 begins to send NLPs, theyare detected by the EDM of the switch. The device that contains theswitch manager 22 must now be booted in a suitable manner. The switchmanager 22 must thereupon activate switch 24 and place it into its basicstate. All FSMs are in the DOWN state after the booting process.

A switch device 14 activates a switch device 24 of the next hierarchylevel below as follows.

If a switch 24 of the next hierarchy level below is to be activated,this is effected by the same mechanism. The hierarchically higher switchreceives from the network manager 20 the request to activate thecorresponding port. It makes no difference to it whether a host 18 or aswitch 24 is connected to the port. The FSM changes into the HOSTSTARTUPstate and the PHY is activated (NLPs are transmitted).

The EDM of the hierarchically lower switch 24 indicates the NLPs andswitch 24 is started up and immediately activates its root port. Thisleads to a change of state from HOST STARTUP to UP in the hierarchicallyhigher switch 24, both sides detect link pulses and the connection isestablished.

A switch device 24 activates a switch device 24 of the next hierarchylevel above as follows.

Host 18 is activated from the outside and in consequence activates itsrespective switch 24. This, in turn, must activate the hierarchicallynext switch 24 above in order to establish a connection to the networkmanager 20. For this purpose, the switch manager 22 must know via whichport it is linked to the next hierarchy level above (it must know itsroot port). For example, a port number is defined which applies globallyfor all switches 24 as connection to the next hierarchy level (e.g. port1). Another possibility would be a memory entry which is specifiedindividually for each switch.

According to the state diagram, the FSM of the root port changesimmediately into the HOST STARTUP state after the booting. Thehigher-level switch is woken by the NLPs sent via the root port.

Deactivating host 18 by the switch device 14/switch 24 occurs asfollows. If a switch device 14 receives the request from the networkmanager 20 to deactivate a host (port) 18, this can also be achieved bythe port state machine. The request by the network managers 20 has theconsequence that the FSM of the port changes from the UP state into theHOST-SHUTDOWN state, the PHY of the port being deactivated (no furtherNLPs are sent). The FSM remains in this state until no further NLPsarrive from the host 18.

The network controller of the host will report a “link fail” as soon asit receives no further NLPs from the switch. This event can be used astrigger for the shutdown process of the host. However, as analternative, the output of the host EDM could also be used since it willno longer indicate any link activity. The precise procedure remainsopen. If the host shuts down, it will stop itself sending NLPs. In theport FSM of the switch, this leads to a change in state from HOSTSHUTDOWN to DOWN. The interface is thus deactivated, the host shutdownand the request is met.

If something goes wrong when shutting down the host and further NLPs aresent by it, the state machine of the switch changes into the ERROR stateafter a defined time and deposits a shutdown timeout as error.

Deactivating of a switch by a switch occurs as follows. If a switch isintended to deactivate a hierarchically lower switch, the mechanismproceeds similarly to the deactivation of a host by a switch. The casewhere a switch deactivates a hierarchically higher switch does not existsince it would cut its own connection to the network manager 20 by thiswhich is impossible by definition.

It does not make a difference to the switch whether a host 18 or aswitch 24 is connected to the port to be deactivated. The hierarchicallylower switch (manager) to be deactivated knows via which port it isconnected to the next hierarchy level above. If it receives no furtherNLPs from this port, this is the trigger for it to initiate shutdown. Bydefinition, the network manager 20 has already switched off all ports ofthe switch 24 to be deactivated before it shuts down switch 24 itself.

Initially, the port FSM changes into the LINK FAIL state since nofurther NLPs are received. From there, the next change of state leadsinto the DOWN state, the interface is now deactivated. The switchmanager can now initiate the shutdown process of the switch and thenshut itself down.

Interactions at the network level—communication between network manager20 and switch manager occurs as follows.

As already discussed, the network manager is responsible for requestingthe switch managers to activate or deactivate their ports. Since thenetwork manager knows the topology of the network and the state of thenodes at any time, it can thus establish any desired configuration ingetting individual hosts or entire part-networks to become activated ordeactivated. This presupposes that every active switch manager has avalid connection to the network manager (root of the tree). If the endpoint of a branch is active, the entire branch must therefore be active.

The manner of communication between the network manager and the switchmanagers is not established. It is the requirement that the networkmanager can inform the switch manager about its intention and the portwhich is involved and that the switch manager 22 can convey messages tothe network manager 20 when one of its connected nodes has beenactivated. The network manager 20 can thus update its state table.

The Simple Network Management Protocol (SNMP), for example, is wellsuited for this. The Interface Management Information Base (IF-MIB) isavailable which, among other things, contains the managed object withthe object ID (OID) (ifAdminStatus). This object specifies the desiredstate of an interface (port). If the network manager has an SNMPcontroller process and the switch managers have in each case an SNMPagent, the network manager 20 can send an SNMP SET packet to the switchmanager 22 and set the object ifAdminstatus to the desired value. Thenotification about when a node has been activated can be carried out viaan SNMP TRAP packet sent by the agent. In response to the TRAP, theswitch manager 22 would have to send back an SNMP GET packet and readout the values of the ifAdminstatus object for each port andcorrespondingly update its state table. Since SNMP also offers amultiplicity of further management options, this basis can also be usedas a platform for further network management.

A less extensive, slimmer method could be to define own wake-up, shutdown and notification frames which contain the relevant port number. Thedisadvantage of the methods consists in that it is not standardized anddoes not offer an existing platform for further management functions.

Host requests are handled as follows. In most cases, an active hostneeds a “dialog partner” with which it can exchange data. As a rule, thenetwork manager knows the existing dependencies between various hostsand will itself activate all necessary network nodes in the appropriateorder.

However, the possibility also exists that a host needs a different hostfor a short term which, however, is currently inactive. The principle ofcentralized management does not provide for a host waking another oneindependently. The host must request the activation of the other onefrom the network manager. The network manager can then decide whether itwakes up the requested host (authorizations could play a role here) and,if necessary, perform the wake-up. As soon as the notification arrivesfrom the “destination switch” that the requested host has beenactivated, the network manager can convey the confirmation to the hostfrom which the request came.

Cascaded switches are extended as follows. It has already been said thateach switch manager must have a path to the network manager, that is tosay there can be no “gaps” in the branches of the tree.

Activation of a node via a switch 24 which is already active if a nodeis to be activated is connected to a switch 24 that can already bereached, the case is trivial. The network manager 20 requests switch 24to activate the corresponding port.

Activation of a branch by the network manger 20 becomes more complicatedif the node to be activated is on an as yet inactive switch or at theend of a branch of inactive switches, respectively. The network manager20 knows the topology and must then wake up each switch 24 along thepath to the destination node sequentially until it can reach thedestination switch and can thus activate the desired node. Thus, theentire branch up to the destination node is activated.

Deactivation of a branch by the network manager 20 of a branch proceedsanalogously. The network manager 20 knows the topology and deactivatessequentially all nodes which are located below the switch 24 actually tobe switched off.

FIG. 3 illustrates the activation of a branch 34 by a user:

If a host 18, which is part of an inactive branch 34 is activated fromthe outside, the “host activates switch” case initially occurs.Considering again the port state machine of switch 24, the recursivepropagation of the wake-up through the entire branch 34 becomes clear:

-   -   The first switch 24-A attempts to set up a connection to the        (not yet accessible) network manager 20 and initially activates        its root port. However, the root port FSM remains in the HOST        STARTUP state until NLPs are received from the next switch 24-B        above.    -   The next switch 24-B above will boot up and will firstly        activate again its root port in order to establish the        connection to the network manager 20. However, it remains in the        HOST STARTUP state until it receives NLPs from its root port,        that is to say from switch 24-C. This pattern continues        recursively up to the first switch 24-Z already active. If the        entire branch 34 was inactive, this would be the highest switch        24 to which the network manager 20 itself is connected.    -   The switch 24-Z, previously active, already has a connection to        the network manager 20 and will respond immediately to the NLPs        of the next switch 24-Y below. At the same time, it will inform        the network manager 20 about the activation of the corresponding        port.    -   Since the next switch 24-Y below now receives NLPs, the FSM of        its root port changes from the HOST START to the UP state and        there is a connection to the next switch 24-Z below and thus to        the network manager 20. Switch 24-Y can now respond to the next        switch 24-X below (the FSM of the port changes from HOST STARTUP        to UP and NLPs are transmitted). At the same time, switch 24-Y        informs the network manager 20 about the activation of switch        24-X.    -   This pattern continues up to the end of branch A so that the        notifications are sent to the network manager in the “from top        to bottom” order (the wake-ups, in contrast, propagated “from        bottom to top” through the branch). This is necessary too, since        a switch can notify the network manager only when it has a        connection to it.

A port state machine is illustrated in FIG. 4.

Starting from a “reset” (or “boot”) state, the alternative events areinitially obtained that the port is not a root port (E0) which leads toa “down” state of the port, or that the port is a root port (E1) whichleads to a “startup” state.

However, the “startup” state can also be reached from the “down” stateby a “wake-up” request (E2) by the network manager by means ofactivating the PHY actions (A0) and timer resetting (A1). If activity ofthe host 18 is lacking and the timer (E3) is running, the port remainsin the “startup” state.

Starting from the “startup” state, the “up” state is reached by a hostactivity (E4) in which the network manager 20 is activated (A2). As analternative, only an “error” state is reached from “startup” when hostactivity is lacking and there is a timeout (E5).

From the “up” state, the “shutdown” state is reached by a “shutdown”request (E6) by the network manager 20, PHY being deactivated (A3) andthe timer being reset (A1).

If the host 18 is subsequently still active and the timer is running(E7), the port remains in the “shutdown” state. If there is no furtherhost activity (E8), the network manager 20 is notified and the “down”state is reached. If, in contrast, there is a timeout while the host 18is still active (E9), the “error” state occurs.

From the “error” state, the “reset” state is reached by a reset (E10) inwhich PHY is deactivated (A3).

As an alternative to the “shutdown” request (E6) a “link fail” state isreached by a lacking link activity (E11) from the “up” state whereuponthe Deactivate PHY action follows (A3) and the “down” state is reached.

This completely describes the port state machine shown in FIG. 4.

In the text which follows, the concept is illustrated by selectedexamples with reference to FIG. 5:

The network is a switched Ethernet that comprises three switches 24-S1,24-S2, 24-S3 to which a plurality of hosts 18 are connected (see FIG.5). The switch managers 22 are switch manager 22-alpha, switch manager22-beta and switch manager 22-tau. Some hosts 18 can be activated anddeactivated from the outside (e.g. by a user or an event) and are called“awakeable” in the text which follows. On the other hand, other hosts 18can only be woken up and deactivated within the network, i.e. on theinitiative of a switch 24 or of another host 18 (not wakeable).

Switch 24-S1 has a special role. It forms the root of the topology treeand its switch manager 22-alpha is at the same time the central networkmanager 20.

In the examples, SNMP is used for the communication between networkmanager 20 and the various switch managers 22. The network manager 20has an SNMP client for sending SNMP packets, the switch managers have anSNMP agent.

Activation of host 18-omicron occurs as follows. This exampledemonstrates the activation of individual hosts 18 in the network by thenetwork manager 20. In the initial situation, the entire network system10 is deactivated apart from the host 18-S1/alpha constructed as centralnetwork device 12. The network manager 20 of this central network device12 would now like to establish a state in which the hosts 18-omicron and18-epsilon are active.

Initially, host 18-omicron is activated. It is connected directly to theroot switch S1 (port S1-1). The network manager 20 accesses the SNMPclient of host 18-alpha and sends an SNMP SET packet to the SNMP agentfrom host 18-alpha. As a consequence, object “ifAdminstatus” for portS1-1 is set to TRUE.

The SNMP agent informs the switch manager of switch 24-S1 aboutifAdminstatus being set to true, which leads to a change in state of thestate machine of the port from DOWN to HOST STARTUP and thus to theactivation of the PHY of port S1-1, whereupon NLPs are sent out. The EDMof host 18-omicron (a network component 16) detects these NLPs andthereupon triggers the booting process of host 18-omicron. As soon asthe network controller of host 18-omicron is active in turn and sendsNLPs, the EDM of the switch 24-S1 detects this and a HOST STARTUP to UPchange in state takes place. In this context, the network manager isinformed that the node connected to port S1-1 has been activated.

Activation of host 18-epsilon (also a network component 16):

Next, host 18-epsilon is also to be activated. The network manager 20knows that it can reach host 18-epsilon via switch 24-S2 and thus viaits port S1-4. It also knows that switch 24-S2 and its switch manager22-beta are still inactive and thus have to be activated first. Firstly,an SNMP SET packet is again sent to the SNMP client from host 16-alpha(in this case the central network device 12) in order to turn on portS1-4. According to “switch activates switch of the next hierarchy levelbelow”, the EDM of switch 24-S2 detects the NLPs, the switch 24 andswitch manager 22 are started up and the root port of switch 24-S2 isactivated. Switch 24-S2 and switch manager 22-beta are now active andthere is a valid connection. The network manager 20 is also notifiedthat the node connected to port S1-4 (that is to say S2/beta) has beenactivated.

To activate also host 18-epsilon, the same procedure is adopted as inthe previous case during the activation of host 18-omicron. The onlydifference is that SNMP client and agent are no longer located in thesame device but the SNMP SET packet is sent to switch manager 22-beta.

Activation of host 18-pi by the user is as follows.

The entire network system 10 apart from switch 24-S1 and switch manager22-alpha (which, at the same time, is network manager 20), will becompletely deactivated again. Host 18-pi is activated from the outside(by a user or an event). The cascade consists of three switches, 24-S3,24-S2 and 24-S1. Host 18-pi firstly wakes up switch 24-S3 and switchmanger 22-tau and waits for NLPs from switch 24-S3. As the first action,switch manager 22-tau will activate the root port of S3 (port S3-1) andwait for NLPs from switch 24-S2.

Analogously, switch device 14-S2/beta will wake up and switch manager22-beta, in turn, will activate the root port of switch 24-S2, that isto say S2-1. Switch 24-S1, which is already awake, thereupon turns onthe PHY of port S1-4.

Switch device 14-S2/beta detects the NLPs from switch 24-S1. The rootport FSM changes into the UP state and the switch manager 22 now beginsto process the NLPs arriving from port S2-4. The FSM of this portchanges into the UP state, the PHY is activated and NLPs are sent back.In addition, the network manager 20 is informed that the node connectedto S2-4 has been activated.

The same process now takes place one level lower with switch device14-S3/tau and port S3-2. As soon as the NLPs have then be answered byhost 18-pi, the network manager 20 is informed that the node connectedto the port S3-2 has been activated.

The wake-up has run through the cascade from bottom to top, but thenotifications to the network manager 20 have done so from top to bottom.

Deactivation of the entire branch 34 occurs as follows. The networkmanager 20 decides that the branch 34 just activated (that is to sayswitch 24-S2, 24-S3, host 18-pi) should be deactivated again. This isdone from bottom to top: the network manager 20 will sequentiallydeactivate host 18-pi, switch device 14-S3/tau and switch device14-S2/beta. If, for example, host 18-epsilon were still active, thenetwork manager 20 would also deactivate it before it shuts down switchdevice 14-S2/beta.

Initially, host 18-pi is deactivated by an SNMP SET packet being sent tothe switch manager 22-tau, the ifAdminstatus object for port S3-2 beingset to FALSE. The FSM of the port changes into the HOST SHUTDOWN state,deactivates the PHY and in this state waits until no further NLPs aresent by host 18-pi either. After that, the state changes to DOWN and thenetwork manager 20 is informed that the node at port 53-2 has beendeactivated.

After that, host 18-alpha sends a further SNMP SET packet to host18-beta in order to analogously deactivate port S2-4. This shuts downthe switch device 14-S3/tau.

Lastly, host 18-alpha sends an SNMP packet to itself in order todeactivate port S1-4. Switch device 14-S2/beta is now also shut down andthe entire branch 34 is deactivated.

Thus, while there have shown and described and pointed out fundamentalnovel features of the invention as applied to a preferred embodimentthereof, it will be understood that various omissions and substitutionsand changes in the form and details of the devices illustrated, and intheir operation, may be made by those skilled in the art withoutdeparting from the spirit of the invention. For example, it is expresslyintended that all combinations of those elements and/or method stepswhich perform substantially the same function in substantially the sameway to achieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements and/ormethod steps shown and/or described in connection with any disclosedform or embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice. It is the intention, therefore, to be limitedonly as indicated by the scope of the claims appended hereto.

The invention claimed is:
 1. A method for activating at least onetemporarily inactive network component of a network system for avehicle, especially a motor vehicle, comprising: transmitting by acentral network device of the network system a signal to a first networkcomponent via a path inside the network system that leads at leastpartially across a network segment of the network system; connecting atleast partially in response to the signal the first network componentand its associated first activation device connected unbranched to atleast one switch device arranged in a path and to an associated secondactivation device; and the central network device addressing theassociated first activation device by the at least one switch device bysending a network function control signal whereby the at least onetemporarily inactive machine network component is activated.
 2. Themethod as claimed in claim 1, further comprising: activating the firstnetwork component by the associated first activation device afterreceipt of the network function control signal; and subsequently thefirst network component sending out a further network function controlsignal to the associated second activation device to confirm theactivation.
 3. The method as claimed in claim 2, wherein the secondactivation device brings the at least one switch device into atransmitting/receiving state after receipt of the further networkfunction control signal.
 4. The method as claimed in claim 1, whereinthe network system is an Ethernet network.
 5. The method as claimed inclaim 1, wherein the network system has a tree topology formed by thecentral network device, the at least one switch device and the at leastone network component.
 6. The method as claimed in claim 1, wherein atleast one of the first network component and the central network deviceis at least part of a control device of a vehicle component.
 7. Anetwork system of a vehicle, configured to activate at least onetemporarily inactive network component, comprising: at least one networkcomponent having an associated first activation device; at least oneswitch device; a central network device connected for signalcommunication to the at least one network component via a path withinthe network system, the path leading at least partially across a networksegment of the network system and the network segment connecting forsignal communication the at least one network component and theassociated first activation device unbranched to the at least one switchdevice arranged in the path and to an associated second activationdevice, wherein the central network device addresses the associatedfirst activation device via the at least one switch device by sending anetwork function control signal.
 8. The network system as claimed inclaim 7, wherein the network system is an Ethernet network.
 9. Thenetwork system as claimed in claim 7, wherein the network system is atree topology formed by the central network device, the at least oneswitch device and the at least one network component.
 10. A motorvehicle comprising: a network system configured to activate at least onetemporarily inactive network component, having: at least one networkcomponent having an associated first activation device; at least oneswitch device; a central network device connected for signalcommunication to the at least one network component via a path withinthe network system, the path leading at least partially across a networksegment of the network system and the network segment connecting forsignal communication the at least one network component and theassociated first activation device unbranched to the at least one switchdevice arranged in the path and to an associated second activationdevice, wherein the central network device addresses the associatedfirst activation device via the at least one switch device by sending anetwork function control signal.